Roller electrode spot welder



July 20, 1954 C. N. ANDERSON ROLLER ELECTRODE SPOT WELDER Filed Aug. 27,1951 1N VEN TOR.

CHA @Les 1v. ,aNoseso/u Patented July 20, 1954 ROLLER ELECTRODE SPOTWELDER Charles N. Anderson, Renton, Wash., assignor to Boeing AirplaneCompany, Seattle, Wash., a

corporation of Delaware Application August 27, 1951, Serial No. 243,771

5 Claims. l

This invention relates to spot welding apparatus and has for its generalobject a relatively simple manual feed machine capable of a much higherproduction rate than was formerly attainable with manual feed machineswhile being capable of operating successfully with work materialsranging widely in thickness and especially with thin sheet metal.

Up to the present most, if not all, sheet metal spot welding operationsin airplane factories and other manufacturing plants striving for largeproduction volume have been accomplished with spot Welders of thereciprocating rod electrode type with manual feed and with or withoutautomatic recycling of electrode operation. Automatic feed machines,apart from their greater cost, have been unsuited to such work becauseof the difhculty with them of selectively controlling Weld locations andweld spacings during any given operation. For instance, if such amachine were set for operating with a particular weld spacing closeenough for ample Welded strength in heavily stressed areas of a piece ofwork, then the spacing selected would be too close for economicalwelding in work areas requiring less strength. The converse would alsobe true as to spacing adjustments optimum for work areas requiringminimum welded strength. On the other hand, conventional rod-electrodeWelders have not given production volume as high as might be desired,even when provided with automatic electrode recyclying, i. e. continuousautomatic reciprocation of at least one electrode to and from the workin timed relation with electric energy applications.

It was observed that a major source of limitation on production rate inthese conventional Welders was the time lost during each total cycle inproducing useless movement of the movable (usually upper) electrode, intraveling into and out of contact with the work at the beginning and endof each welding cycle. This lost time represented a large part of thetotal cycle of the machine and served no purpose other than to provideclearance to feed the work in the period between successive welds. Inany conventional machine of a given size and capacity employing areciprocating spot welding electrode this lost time could not be greatlyreduced by any practicable changes in design contemplating fastermovement of the electrode, due to inherent inertia of the movingstructure, lost motion incurred in displacing necessary pressurecontrolling springs, and the limited mechanical power available.

Moreover any attempt to increase the attainable operating frequency ofsuch former machines by reducing the period of lost time consumed inmovement of the rod electrode through the route oi shortening its strokeonly created work clearance problems. Inadequate clearance or spacingor" the rod electrodes from the work in the periods between successiveelectrode contacts therewith caused rubbing and chang and made feedingand guiding the work difcult and tiresome. Thin and flimsy work tendedto buckle because of electrode drag.

The present invention is directed to the provision of a high productionmachine of the automatic recycling electrode type, and is especiallyaimed at accomplishing this object as economically as possible bypermitting incorporation of major components and assemblies ofconventional machines where desired. With a conventional machinemodiiied in accordance with the present invention it proved possible tonearly triple the rate of production formerly attainable, especiallywith thin sheet metal work, and to produce better work. Moreover, longerwearing electrodes requiring less frequent dressing than conventionalrod electrodes and posing simpler cooling problems resulted.

In the improved machine the conventional rod electrodes are replaced byidler roller electrodes. The work is fed manually in the usualstep-bystep manner and at the desired constant or variable rateaccompanying operation of the automatic electrode recycling apparatus ofthe machine. Provisions of the improved machine ior automaticallyholding one or both roller electrodes against rotation accompanyingelectrode pressure applications during actual welding `periods functionto prevent untimely shifting of the work by the operator and weakeningof the welds produced. However, in the work-feed periods between actualwelding periods the roller electrode braking action is automaticallyremoved accompanying reductions of electr-ode pressure, so that the workmay then be fed freely between the roller electrodes.

A basically important advantage of the improved manual feed automaticelectrode-recycling spot Welder is the considerable shortening of themechanical stroke of the electrode reciprocating apparatus now permittedwithout causing frictional drag and work buckling, as the rolling actionof the electrodes permits them to remain in contact with the work at alltimes. A higher recycling frequency, hence a higher work output rate, isthereby achievable by saving time lost previously in retracting andadvancing electrodes, while preserving all the flexibility and otheradvantages of the former type manual feed machine. it is merelynecessary that electrode pressure on the work be reduced after each weldin crier to remove the braking effect mentioned above and permitadvancing. the work for the next weld'. infact the steadyihgvv effectand rolling support of the work by roller electrodes greatly facilitatesfeeding and guiding the work-- accurately through the machine. In theimproved machine there is no tendency for and flimsy work to bucklebecause of rubbing oi former rod electrodes thereon when electrodeclearances were reduced in previous machines, and instead guidance ofthe work is actually iacilitated by the rolling contactn'ow provided.

Preferably braking is applied to one or both electrodes in the improvedmachine hy a separate friction brake of' the electrode-pressure actuatedtype, for instance, or in some cases by the mere hearing friction' oftheroller electrode shafts alone accompanying welding pressure of theelectrodes on the work. It should be understood', however, that otherautomatic cyclical braking devices could be usedv for the purpose, thosedescribed herein being merely illustrative.

The yforegoing andY other features= objects and advantages of theinvention, including certain details of construction of preferredembodiments thereof,. will become more' fully apparent from thefollowingV description by reference to the accompanying drawings. TheseAdrawings are intended as illustrative of the` preferred form of theinvention, but are by no means the only applications or embodimentsthereof which may be' employed.

Figure l is a: simplified sidev elevation of a spot Welding machineincorporating the invention, portions of the machine being' broken awayand certain portions illustrated schematically.

Figure 2 is a simplified front elevation view on an enlarged scale ofthe roller electrodes and their supports in such a machine.

Figure is a simplified front elevation View on a larger scale of thekroller electrodes and a friction brake in theV lower electrode support.

Figure 4 is a side elevation of the electrodes and supports appearing inFigure 3.

In VFigures I and 2 theY upper roller electrode ity is tree to rotate onits supporting shaft i2, mounted between the arms of a support lil'.This support in turn is carried by a reciprocative head it mounted onthe lower end of a piston' rod It. The rod 18,#in turn, is guided forvertical reciprocation in the actuating cylinder 2li and retractingcylinder 22, both usually pneumatic, and containing pistons, as inconventional spot welding machines of the type' previously mentionedherein. The details of such machines and of the retraction and actuatingcylinder mechanisms, together with automatic controls therefor are wellknown, so thatV a particular illustration or description l'u'reiny ofsuitable techniquesY involved is deemed unnecessary'. Continuedautomatic recycling of" the electrodes rnechan'ic'ally and electricallyis' accomplished in the illustrated machine simply oy maintaining thepedal 2l in depressed position to operate the automatic controls shownsimply as a unit 23 in the ligure. Scaky Patents 2,415,703 (Feb- Y ruaryl1, 1947) and 2,474,866' (-Jul'y 5, 194e) illus- Gli a tornatically inrecurrent manner, and disclose means by which electrode reciprocationmay be timed therewith. Other types of control apparatus accomplishingthe desired ends will he obvious.

The lower electrode 2t is freely rotatable on its supporting shaft Slimounted between the arms of the support 3 This support` is fixed on theupper end of a cylindrical post' 3? slidably received in the supportingtube 32 and restrained against rotation therein by a slot andpinconnection 38 (Figure 2). A compression spring is received in the lowerend of the tube 32 and' acts upwardly therefrom against the post 3l tourge the lower electrode 26 against the under side of the work W. Theextension sliarrk' 5E of the is supported by a horizontal arm structuret3 on the machine frame to iocat'e the lower roller electrode 2B exactlybelow the upper roller electrode I0, as shown. A setscrew dithreadedthrough' a bore in the reciprocating head IS holds the extensionshank i5 of the upper electrode support in nxed position relative tosuch head, but may be loosened to adjust the position of upper electrodei@ up or down relative to the head. A sirnila setscre'w f3 threadedthrough a Toore in the lower electrode support arm it engages extension3l but may be loosened to permit simi..r adjustment of the lowereiectrod'es position, up or down.

IThe reciprocativ'e head' i5 is initially' at its upper limit of travel'effected by retraction of piston rod' t8. Electrode it is' then in itselevated position but remains in contact with the worlr' W due to theupward pressure or ther lower electrode 25S against' the lower face' of.the work caused oy the spring Se' housed in the lower electrode' supporttube 32, as shown; Pressure of the electrodes against opposite faces ofthe wor-lt` is then a being established by the residual torce or springSil in the elevated positionfof upper electrode' i'. At this time thework W' may between the electrodes it and' 28 without appreciableresistance as such electrodes roll freely on the work. The operatorestablishes the rate of advance of the work at this time.

Such manual feed movement of the work is subsequently stoppedautomatically by friction braking in the machine illustrated Figure l.Such braking occur when the automatic re'- cycling apparatus 25 causesactuating cylinder 2a to depress the upper electrode i@ and workcontacted thereby downwardly against the progressively increasingresistance' oi. spring tt in reaction to downward yielding of the lowerelectrode under' the advance of the upper electrode. The' frictionbraking edect mentioned' results simply from irictional drag between theroller electrodes l@ and 28 andV their respective supporting shafts E2and Se when pressed against eachother bythe force of compressed spring3e in the descended position of upper electrode it. friction issufficient ordinarily to prevent any further movement of the work in thelinek or" feed, so that shifting. of the work cannot occur during' theensuing actual weld cycle and spoil the quality of the weld produced.Electrical energy is supplied to the electrodes through their conductivesupports and' conductors 36 and 33 from a suitable source (not shown)vautomatically upon application of electrode Working pressure to thework, i. e. upon full' descent of upper electrode The residual force ofspring in the uppermost position of the electrodes is established by thelength of stroke of upper electrode l0. This force, of course,represents the minimum electrode pressure against the work andordinarily is adjustable in machines of the type described, as byadjusting the length of stroke of the upper electrode, means for theadjustment being symbolized by the control knob in Figure 1. Theduration of the electric energy impulse supplied to the electrodes isalso conventionally adjustable in such machines, means for itsadjustment being symbolized by the control knob 42 in the gure. Thisperiod of time, during which the work is being heated by flow of theelectric current between the electrodes, is selected in accordance withthe thickness of the work.

At the end of the heating period selected by adjustment of knob 42, theelectrical circuit is automatically opened by control apparatus 26.However, the upper electrode I0 is not immediately raised by theautomatic recycling apparatus upon deenergization of the electrodes, asit is 'desirable to maintain electrode pressure on the work for a shortperiod of time thereafter during which time the work is permitted tocool and the weld to set. If desired, this period of time may beadjusted in accordance with the nature of the work by suitable meanssymbolized by the third `control knob 44 in Figure l.

y At the end of the time period just mentioned, the control apparatus 26 automatically actuates retracting cylinder 22 to raise the electrodel0 into elevated position and thereby reduce the electrode pressure onthe work to relieve the roller electrodes of their shaft friction. Theelectrodes will then roll freely and, for a predetermined period oftime, permit the operator to advance the work W readily between them byanother increment for the succeeding welding operation. Such operationis initiated automatically by the recycling control apparatus 26 at theend of the work feed period by again applying pressure and electricalenergy to the electrodes. The work feed period may be xed or may be madeadinstable, as desired, involving familiar devices in either case, acontrol knob being shown in Figure l to represent means for thisadjustment.

In Figures 3 and 4 the modied electrode arrangement differs irom that inthe preceding iigures with respect to the manner in which electrodebraking is accomplished. In the modified form a more positive brakingaction applied to the lower electrode is achieved by use of frictionbrake shoe 555, which bears against the lower I periphery of lowerelectrode 28 as a result of electrode pressure during the weld cycle ofthe machine. brake shoe 5G is suspended under the lower electrode 28' bypins 52 received in notches in the upper ends of the xed supporting yoke513. This `yoke is fixed on the tubular shank extension iii of the lowerelectrode support and may be adjusted up or down along such extension byloosening its set-screw 56. The shank extension 4 i in turn is slidablyadjustable in the horizontal lower electrode supporting arm 43', aset-screw 4S being provided as in the previously described form of themachine. The tubular shank extension 4i is closed at its lower end by ascrew plug 5S, which has a tapped bore to receive the bolt fill. Thelatter carries a plunger E2 on its upper end inside the tubularextension 4i' to constitute an adjustable stop therein for the spring 30which bears upwardly against the post 31 carrying the lower electrodesupport 35. When the upper electrode I0' is raised and lowered,preloaded'spring 36 expands and contracts as post 3l slides up and downin the tube 4 and maintains both electrodes in contact with the work.

When properly adjusted for operation, the position of the brake shoe 5Gin relation to the axis of roller electrode 28 in the latters elevatedposition, is such that the desired pressure of a contact between thelower periphery of such electrode and the brake shoe is established atthe instant the electrode reaches its desired lowermost position duringdescent of the upper electrode i0 into its depressed position forwelding. In other words, the yoke 54 is positioned along the tubularmember lll so that the brake shoe 5t will not prevent full descent ofthe electrodes under actuation of the automatic recycling apparatus ofthe machine, but will nevertheless firmly engage the electrode rim whenthat position is attained. Spring 3B' serves the same function as spring3i! in the preceding described form of the machine.

In Figures 3 and 4 the electrodes are watercooled in accordance with ausual practice involving suitable heads 56 and suitable inlet and outlethoses or conduits 58 and 59 connected thereto for supplying coolingwater to the hollow electrode interior through hollow electrodesupporting shafts. The mere use of roller electrodes, however, evenwithout separate cooling provisions, affords advantages overconventional rod electrodes in machines of the type described because ofthe continual presentation of new electrode surfaces to the work asprogressive Welding takes place. Moreover, dressing' of rollerelectrodes is much less a problem than in conventional rod typeelectrode machines.

The main advantage, however, or" the improved machine lies in the muchgreater production volume which may be achieved by permitting the lengthof stroke of the reciprocating apparatus to be reduced to a minimum,representing merely the movement necessary to deflect the spring 3i? orBil sufficiently for attaining the desired maximum and minimum pressuresthereof. A larger proportion of the total operating cycle of the machineis thus put to effective use and the electrode actuating mechanism canbe recycled much more rapidly than heretofore. In the operation of theimproved machine the roller electrodes may actually remain in continuouscontact with the work, although expansion and contraction of the spring(3 or Ss') will cause the desired variation in electrode pressure, sothat at minimum pressure the work may be advanced readily between theelectrodes which roll freely thereon, whereas at maximum pressure thework pieces are held together for welding and the electrodes are brakedagainst any movement which the operator might otherwise cause at thewrong time to disturb the weld. The continued contact of the electrodeswith the work and the use oi roller electrodes are both factors whichgreatly facilitate the guiding of the work along a desired path andthereby improve the duality of welding as well as greatly increasing thevolume of work that may be done with the improved machine.

I claim as my invention;

l.. A manual feed spot welding machine comprising upper and lower rollerelectrodes and supports therefor, means comprised in said supportsrotatively supporting said electrodes to roll freely on the work fedtherebetween, cyclically operating means operable to reciprocate atleast one of said electrode supports for advancement toward retractionfrom the other intermittently, re-

silient means interposedy operatively between one of. said` supper sandv its elerfuodek and deneetable progressively in response-toadvaneement of1 said reciproeative support to establish progressivelyincreasing electrode pressure onl the work during such advancement,means for adjusting. the stroke of suon oyclieallyy operative means andthereby the deflection limits of said resilient means to establish themaximum and minimum electrode pressures on the Werk during reciproca.-tion` or" said reoiprocative support, Without actually breaking physicalcontest of said eiectrodes with the work, and normally released brakemeans cooperating with at least one of said electrodes to apply arotation-braking ieetthereto automatiealiy inl response to positioningof said cyclicz ly operativerneans in' applying maximum electrodepressure to the Work.

2. 1n a spot welding machine, upper andV lower freely rotatable rollerelectrodes, means supporting said electrodes to receive worktherebetween, means cooperating with said support including pressureapplying means operable to increase and decrease electrode pressure onthe work cyeli'eally Without breaking physical Contact therebetween, andbrakey means cooperating with at least one such electrode to applybraking force thereto automatically in response to attainment of maximumelectrode pressure against the work, thereby preventing si ifting of thework during weld cycles, and toremove suoli braking force automaticallyin response to a reduction of the electrode pressure below such maximum,thereby freeing the braled electrode for rolling freely on the Workbetween Weld cycles.A

3. In a manual feed spot welding machine of the type having upper andlower electrode supports and means for reciprocating at least one ofsaid supports cyclieally toward and from the other intermittently intimed relation to electric energy applications to electrodes carried bysaid supports; upper and lov-,fer roller electrodes carried by therespective upper and lower electrode supports adapted for rollingContact with Work being advanced therebetween, one of said electrodesbeing mounted onv its support to permit relative reeiprocationtherebetween in the line of movement of said reoiprocative support,yieldable resilient means. interposed between saidlatter rollerelectrode and its support substantially continuously maintaining Saidelectrode pressed against the Work and the. Work against the opposingeleetrode by variable deflection o1". said resilient means elected byreoiprocation of the reeiprocative electrode support, and brake meanscooperating withA at least one of said supported electrodesautomatically increasing resistance to advancement of the Work betweensaid roller electrodes by movement of said reciproca-tive support towardthe work and` decreasingV such resistance by reverse movement of saidreciproeative` support.

4. The manual feed spot welding machinel Cleiined iny claim 3, whereinthe automatically acting brake means comprises antifrietional rotationalsupport bearing means for at least one ofi the roller electrodes, saidbearing means having coacting bearing surfaces inherently imposing ma.-terially varyingrotational friction on such electrede eieeted by thevarying electrode pressure on the Work accompanying variable deflectionof the resilient means.

5. The manual reed spot Welding machine denned in claim 3, wherein theautomatically acting brake means comprises rictional Contact meanssubstantially xedly motuitedV on the electrode support carrying theresilient means-in operative position ythereon for intermittentlyfrictionally engaging the associated roller electrode aecompanyingintermittent reciprooation of the reciproeative support toward the Work.

References Cited in the le of this patent UNITED ST TES PAIEN'ISV NumberName Date 1,315,239 Pierce et al Sept. 9, 1919 1,438,867 Schroder Dee.l2, 1922 1,778,628' Eckman Oct. 14, i930 2,523,985 Lavallee Dec. 3, 19352,211,185 Weston Aug. 1'3, 1940 2,284,851 Tiedeman June 2, 19422,322,795 Fentress June 29, 1943 2/ii5,798 Sciaky Feb. l1, 19472,474,856 Seiaky July 5, 1949

